Creatine Kinase

 Creatine Kinase (CK, EC 2.7.3.2), an enzyme important for energy metabolism in cells of high and fluctuating energy requirements, catalyses the reversible transfer of a phosphoryl goup from phosphocreatine to ADP. We have solved the structure of the octameric mitochondrial isoform, Mib-CK, which is located in the intermembrane compartment and along the cristae membranes. Mib-CK consumes ATP produced in the mitochondria for the production of phosphocreatine, which is then exported into the cytosol for fast regeneration of ATP by the cytosolic CK isoforms. The octamer has 422 point-group symmetry, and appears as a cube of side length 93 angstrom with a channel 20 angstrom wide extending along the four-fold axis. Positively charged amino acids at the four-fold faces of the octamer possibly interact with negatively charged mitochondrial membranes. Each monomer consists of a small alpha-helical domain and a large domain containing an eight-stranded antiparallel beta-sheet flanked by seven alpha-helices. The conserved residues of the CK family form a compact cluster that covers the active site between the domains.

This view shows the beta sheets in black. This view shows the alpha helices in blue. This view shows the amphipathic alpha helix element along the surface of the protein in pink in a single subunit.

Creatine kinase - brain
3drb, 3dre, 3b6r – hB-CK β chain – human

1qh4 – cB-CK - chicken

Creatine kinase – mitochondria
2gl6, 1qk1 – hMIB-CK

1crk – cMIB-CK

Creatine kinase – muscle
1i0e – hM-CK

2crk - rM-CK – rabbit

1u6r – rM-CK (mutant)

1vrp – M-CK + creatine derivative – Torpedo californica

Creatine kinase – retinal
1g0w – CK - bovine

Reference: Fritz-Wolf K, Schnyder T, Wallimann T, Kabsch W Structure of mitochondrial creatine kinase. Nature. 1996 May 23;381(6580):341-5.